An intensive effort directed at improving the prevention and treatment of acquired immunodeficiency syndrome (AIDS)-associated opportunistic infections continued. Cytomegalovirus (CMV)-IG (Cytogam) did not decrease CMV viruria in treated patients and was shown to be unlikely to be of benefit as prophylaxis against disease caused by CMV. Evaluation of HPMPC, a nucleotide analog, for possible use as in the prevention or treatment of CMV disease continues after finding significant nephrotoxicity at higher doses but a long duration of activity possibly permitting infrequent dosing with concomitant probenecid to decrease toxicity. An on-going blinded Phase I/II study of sparfloxacin, azithromycin, and the combination will provide safety, pharmacokinetics, and efficacy assessment of these agents for the treatment of M. avium complex infection; a salvage regimen will assess these agents plus ethambutol and clofazimine. A safety and pharmacokinetic assessment of levofloxacin, a quinolone with potential utility in the treatment of tuberculosis is planned. Studies on atovaquone (BW566C80) continue, and the efficacy and pharmacokinetics of a new suspension formulation is being assessed for use in the treatment and prevention of pneumocystis pneumonia. We have shown that the addition of pyrimethamine to dapsone for weekly use for the prevention of pneumocystis pneumonia does not change the pharmacokinetics of dapsone. An assessment of atovaquone plus pyrimethamine for the treatment of cerebral toxoplasmosis continues. Atovaquone was not effective for the treatment of cryptosporidiosis or microsporidiosis. The role of Demodex, a mite, in AIDS-associated dermatologic disease is being assessed. The epidemiology and clinical and immunological manifestations of patients with idiopathic CD4+ T-lymphocytopenia were assessed; the disorder is likely to be multifactorial in origin and no evidence of a retroviral etiology was found.